Spatially programmable microelectronics process equipment using segmented gas injection showerhead with exhaust gas recirculation

ABSTRACT

A multizone, segmented showerhead provides a gas impingement flux distribution which is controllable in two lateral dimensions to achieve programmable uniformity in chemical vapor deposition, in plasma deposition and etching and other processes. Recirculation (pumping) of exhaust gases back through the showerhead reduces intersegment mixing to achieve a high degree of spatial control of the process. This spatial control of the impinging gas flux distribution assures that uniformity can be achieved at process design points selected to optimize materials performance. Spatial control also permits rapid experimentation by enabling the introduction of intentional nonuniformities so that combinatorial data from across the wafer/substrate provides results of simultaneous experiments at different process design points. This ability is useful for process tuning and optimization in manufacturing or for rapid materials and process discovery and optimization in research and development.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. §119(e) of U.S.Provisional Application Ser. No. 60/220,231, filed Jul. 24, 2000 andunder 35 U.S.C. §120 of PCT Application Ser. No. PCT/US01/23137, filedJul. 23, 2001.

FIELD OF THE INVENTION

The invention relates to processes which are used to deposit thin filmsof materials by processes such as chemical vapor deposition (CVD), inwhich chemically reactive gaseous species are introduced into theprocessing environment under controlled conditions of temperatures, gasflow and pressure, and in some cases additional plasma or opticalexcitation to cause the deposition of desired materials in thin filmform on a substrate surface such as a semiconductor wafer. Thedeposition occurs because of chemical reactions between the gaseousspecies, usually involving reactions on the surface where deposition isdesired, but sometimes involving reactions which occur in the gas phaseand lead to formation of new species which then deposit on the surface.

BACKGROUND OF THE INVENTION

CVD is a widely used unit operation in the semiconductor manufacturingindustry for thin film device production. The continuing reduction ofdevice feature size and the development of new microelectronic deviceshave increased the demand for new electronic materials which meetspecific materials performance objectives. Common modes of operationinclude (1) thermal CVD, in which the reaction requires only thermalenergy (heating) to proceed, (2) plasma CVD, where a plasma discharge inthe gas phase promotes the deposition reaction, and (3) others such asphoto-CVD, where the deposition reaction is stimulated by opticalexcitation. To obtain the desired properties in the deposited thin filmsof metal, insulator, or semiconductor materials, various combinations ofgases and process parameters are required. While selecting these optimalcombinations has long been a challenge, to meet the demands of featuresize reduction and device performance, the challenge is even greatertoday as fundamentally new and more complex materials and CVDchemistries are required, both for active devices (e.g., high dielectricconstant insulators for FET gates) and for advanced interconnections(including low dielectric constant insulators, copper metallurgy, andmetal nitride diffusion barrier layers).

Competitive manufacturing of semiconductors imposes a major additionalrequirement on CVD processes in the form of manufacturing performance.Silicon wafer sizes are being increased from eight inches to twelveinches diameter in order to reduce the cost per chip, where chips are oforder 1 cm² area each. This increase in wafer size means more than twicethe number of chips are now produced per wafer processed. However, theproperties of each chip on the wafer must be virtually identical,requiring each process to exhibit uniformity of its metrics across thewafer, e.g., to within 1%. Furthermore, the processing rates must besufficiently high for rapid deposition and high throughput, as neededfor cost minimization. Similar considerations apply in other CVDapplication areas, such as plasma CVD processing of flat panel displays.Besides plasma-enhanced CVD, plasma etch processes are widely exploitedfor etching of materials, especially directional etching as needed forthe fabrication of submicron device and interconnect structures andpresent similar problems and consideration.

The various CVD and plasma process modes, described above, have been andare regularly employed in the manufacturing of advanced products. Wherethe products entail a large area, as in the case of large silicon wafersfor semiconductor chips or large glass panels for flat panel displays,the materials performance requirements must be met across a wide spatialextent (8-15 inches) and specified spatial uniformity demands formanufacturing performance.

The conventional approach to achieving simultaneous materialsperformance and across-wafer uniformity for manufacturing is to designthe CVD equipment for single-wafer processing so that gas fluxes impingeas uniformly as possible across the wafer. To attempt to obtain maximumuniformity of gas impingement, some or all of the gases are delivered tothe wafer through a showerhead, consisting of a flat plate parallel toand near the wafer surface. The gas passes through a high density ofuniformly spaced small holes in the showerhead, thus distributing thegas flow as uniformly as possible across a large diameter wafer. Inaddition, reactor design components—including chamber, wafer position(and rotation), pumping, heating, and gas inlet—are constructed toattempt to maximize uniformity in terms of 2-D cylindrical symmetryabout the wafer.

Various showerhead designs have been developed to attempt to generateuniform gas flow patterns over the wafer surface or for uniform filmdeposition. The requirement of across-wafer process uniformity has beena major driving force for the industry trend to single-wafer processingand the delivery of gases through a showerhead in relatively closeproximity to the wafer surface (from about 2 to 20 mm).

For plasma processing equipment, the power distribution means used togenerate the plasma must also be designed to attempt to produce uniformeffects across the wafer. Much of plasma processing equipment today issingle-wafer. For reactive ion etching and for plasma CVD, gas isintroduced through a showerhead parallel to and near the wafer surface.This showerhead serves to distribute the reactant gas species in arelatively uniform manner and also as a counterelectrode for the plasmadischarge, with the wafer attached to the other electrode.

Known single-wafer CVD and plasma process equipment using showerhead gasdelivery provides a reasonably high degree of symmetry to the process.However, because the gas is introduced as uniform flux but is pumpedaway at the edges of the wafer, the deposition symmetry is radial, sothat nonuniformities are experienced primarily in the radial direction,e.g., thicker films result in the wafer center region relative to theedges. Because the deposition reaction consumes the impinging reactantspecies, the flow of gases radially across the wafer leads to radialnonuniformities, the extent of which depend on the particular chemicalspecies in use.

A more flexible design to achieve increased radial uniformity forcomplex CVD chemistries involves a three-zone showerhead as disclosed inU.S. Pat. No. 5,453,124 to Moslehi et al. which has been used fortungsten CVD. In this system, gas is introduced from three independentlycontrolled concentric annular rings, each of which features individualzone feed gas mass flow controllers with potential for real-time controlof process gas flows to each annular segment. The center region iscircular, while the outer two are doughnut-shaped. By changing the gasflows in one zone relative to another, one can attempt to alter radialprofile of deposition rate.

In practice, this has seen limited use for depositing metal compoundbarrier layers, using a single feed gas and with manually switched flowconductance elements to shorten development cycle time for new processequipment. Although this design has been able to achieve some improvedradial uniformity, it still presents significant drawbacks in that itpresents a single fixed rather than modular construction, it does notprovide for exhaust gas sampling through or real-time sensing in theshowerhead, it only permits control of processed gas flows to fixedannular segments, and due to the fact that the gas is pumped away at theedges of the wafer, significant intersegment convective mixing occurs.

Other approaches to controlling process uniformity have been directed toattempting to control spatial distribution of process variables otherthan gas flow. In rapid thermal processing (RTP), wafers are heatedrapidly to reaction temperatures and maintained at these temperaturesbriefly to accomplish annealing, thermal oxidation, or CVD. In RTP, thekey issue is temperature uniformity, both during the reaction and duringtemperature ramp-up. To compensate for radial temperaturenonuniformities during RTP (associated primarily with different heatloss rates at the wafer edge cf. its center), multizone lamp heatingarrays have been employed. Radial nonuniformities present a problem inplasma processes as well. Radially symmetric, tunable electrode elementssuch as those disclosed in U.S. Pat. No. 5,716,486 have been proposed tocontrol both process uniformity and the steady-state particle trapswhich are formed in plasma processes. In all these cases, the equipmentdesign advances have addressed the compensation of only radialnonuniformities.

Despite prior advances, CVD and plasma processes continue to face amajor challenge in achieving uniformity of thin film layers andmicrostructures across the wafer. The first problem is to achieve suchuniformity in the product (silicon wafer, flat panel display, etc.) byappropriate design and operation of the processing equipment, so thatdesired product performance is attained simultaneously with theuniformity needed for efficient and economical manufacturing. Thisproblem is exacerbated not only by the continuous reduction ofmicrofeature sizes to be manufactured on substrates (e.g., wafers,panels) of increasing overall size, but also by important technologytrends and manufacturing considerations in the industry.

One such trend is the prominence of new materials and processes in theindustry. For silicon chips, ultrasmall devices now require insulatorswith dielectric constants much larger than that of conventional silicondioxide. The solutions now being widely pursued are complexmulticomponent materials such as barium strontium titanate, strontiumbismuth titanate, or tantalum oxide, materials which may require dopingas well. These materials require CVD processes for manufacturability,but their intrinsic complexity (three to five chemical elements)exacerbates the challenge in both process development andmanufacturability. For interconnection technology, low dielectricconstant materials are being heavily pursued, in part through CVDprocesses, with similar challenges, along with new materials (metalnitrides for barrier layers, copper for wiring) for the metalliccomponents. The materials complexity involved in deposition reappears inthe challenge of etching these materials using plasma processes.

Another trend is the difficulty in co-optimizing materials andmanufacturing performance since they often present competingconsiderations. Given a process chemistry, the design point which isbest for materials performance may yield poor uniformity in a specificreactor (or indeed in most or all reactor configurations), while processparameters which achieve high uniformity may produce poor materialsperformance. Hence it is a common problem that materials performancemust be compromised to achieve acceptable manufacturing performance(uniformity). Another trend is the escalating cost of manufacturingprocess equipment, which now dominates the cost of manufacturingfacilities.

In the face of this, it is crucial to use the equipment as efficientlyas possible, and in particular to minimize the time in which theequipment must be dedicated to testing process development andrefinement as opposed to production of completed products. However, thechallenge of new materials places an even heavier burden onexperimentation to identify suitable process parameters and recipes touse these new materials. Given these strongly competing considerations,rapid materials and process development, therefore, is increasinglyimportant from a cost perspective. In addition, enterprise costsescalate because the lifetime of equipment is limited to only one or twotechnology generations since they can be readily or economically bemodified after the time an entire new equipment design cycle must becarried out and underwritten.

The use of spatially-programmable process parameters within equipmentdesign for CVD and plasma processes has the ability to significantlyimprove this situation because spatially-tunable process parameterscould be exploited to assure uniformity over a wide range of nominalprocess design points. In particular, multizone showerheads can ensurethat uniformity is obtained at CVD or plasma process conditions desired.However, as embodied in prior known multizone showerheads, severalimportant problems have not yet been solved, or explicitly recognized.

First, interzone mixing sharply diminishes the spatial control which isachievable. For example, the three-zone CVD showerhead design disclosedin U.S. Pat. No. 5,453,124 involves the flow of gas from the wafercenter across the outer regions of the wafer. As a result, the impingingfluxes in the outer wafer radial positions are directly influenced bythe extent of reaction and the impinging gas flow at the center of thewafer. This mixing also has the effect of reducing the resolutioncapabilities of gas composition sensing techniques that rely on gassampling at discrete locations in the gas phase.

Second, spatial programmability of the process is only accomplished inthe radial direction. In reality, other sources cause non-radialnonuniformities as well, from the asymmetries of gas flow due toupstream and downstream equipment geometry, to pattern-dependentreaction and depletion caused by the fact that the patterns and patterndensity of microstructures on the wafer vary with position.

Lastly, rapid materials and process experimentation is not achieved.Although three zones in the showerhead may allow better control ofuniformity, substantial experimentation is still required, and theinformation contained from varying the relationship of the three zoneswill not substantially accelerate process learning (in the analysis ofboth real time sensing and post processing metrology data). Only threezones are involved and the interzone mixing affects the informationcontent in a way which depends on the unknown process chemistry.

The shortened time scales for products in these industries demand morerapid process and product development. In an environment of newmaterials and processes, this presents a major difficulty, because muchexperimentation is required, and little fundamental knowledge exists toguide the materials and process development activities. No matter howefficient the design of such experiments may be, the complexity of thenew materials combinations to be considered places a heavy burden oncomprehensive experimentation which is costly and time-consuming. Andeven for conventional materials and processes, significantexperimentation is required both in development and in manufacturing inorder to optimize individual processes for materials performance andmanufacturing uniformity, and to adjust the design points for severalprocesses to a system-level optimum as required for process integrationand yield.

A fundamental limitation in known conventional experimentation, both indevelopment and in manufacturing, is that many wafers must be processedto acquire an adequate picture of materials and process performance.With single-wafer processing already a dominant trend, industry hasbegun to show great interest in the development and deployment ofadvanced process control methods which can assure wafer-to-waferrepeatability in manufacturing. Given this concern, it is clear thatsequential processing of multiple wafers incurs inaccuracies associatedwith wafer-to-wafer variation of process and equipment, presenting afurther obstacle to rapid experimentation. The demand for new, morecomplex materials and processes further exacerbates this problem, but atthe same time it opens the door to thinking about strategies for majorimprovement. One example is that of combinatorial methods, in which manyversions of a material are produced in parallel, with gradients ofstoichiometry intentionally created across an array of samples.Additionally, few solutions have been proposed to measure uniformitythrough in-situ and/or real-time sensors, and none for CVD.

It is, therefore, apparent that there is a substantial need in the artto achieve a substantially higher degree of control of processuniformity and to accelerate the process development and optimizationcycle by minimizing the experimentation required.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to produce highlycontrolled spatial distributions of impinging gas fluxes for CVD, plasmaand other processes in microelectronics manufacturing equipment. It isanother object to enable process uniformity across the wafer/substrateover a broad range of desired process design points, thereby achievingcompatible co-optimization of both materials and manufacturingperformance. It is yet another object of the present invention toachieve accelerated experimentation and process development by enablingcontrolled nonuniformity across the wafer/substrate, so thatcombinatorial methods provide information on multiple experimentaldesign points in each actual experiment on a single wafer. It is afurther object to facilitate sensing by gas sampling and installation ofother wafer and process state sensors directly above the wafer. It isstill a further object to enable the modular design of process gasdelivery showerhead devices. It is another object of the presentinvention to provide each segment of the showerhead with both a gasinlet and a gas exhaust capability that significantly minimizesintersegment mixing. These and other objects of the present inventionare realized by a multizone programmable showerhead and method for usein microelectronics processing that allows gas flow rates andcompositions to be independently controlled with in each zone or segmentwithout any significant intersegment mixing of gases. In preferredembodiments, each segment is provided with both a gas inlet and a gasexhaust capability that significantly minimizes intersegment mixing.Further preferred embodiments include modular selectively connectedshowerhead segments and real time gas and optical sampling mechanismassociated with each segment which permit collection of real time dataconcerning processing.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional objects and advantages of the inventionwill become more apparent as the following detailed description is readin conjunction with the accompanying drawing wherein like referencecharacters denote like parts in all views and wherein:

FIG. 1 is an elevation schematic showing in cross section a prior artmultizone programmable gas injector showerhead design.

FIG. 2A is a schematic drawing of the prior art showerhead designillustrated in FIG. 1.

FIG. 2B is a schematic drawing of the flow field of the prior artshowerhead design illustrated in FIG. 1.

FIG. 3A is a schematic drawing illustrating a preferred embodiment ofone segment of a showerhead design of the present invention.

FIG. 3B is a schematic drawing illustrating the flow field for twoneighboring showerhead segments of the type illustrated in FIG. 3A.

FIG. 3C is a schematic drawing illustrating the temperature field forneighboring showerhead segments of the type illustrated in FIG. 3A.

FIG. 4 is a top view schematic drawing illustrating a preferredembodiment of a showerhead design of the present invention.

FIG. 5 is a cross-sectional schematic view of a preferred embodiment ofa segmented showerhead system for CVD and plasma process applications ofthe present invention.

FIG. 6 is a flow diagram illustrating the methodology for using thesegmented showerhead design to incorporate intentional nonuniformityacross a substrate.

FIG. 7 is a schematic drawing illustrating a preferred embodiment of apre-segment showerhead system of the present invention.

FIG. 8A is a portion of the computer program listing for simulating theeffects of using the design of the present invention on a substrate.

FIG. 8B is a continuation of the computer program listing in FIG. 8A.

FIG. 8C is a continuation of the computer program listing in FIG. 8B.

FIG. 8D is a continuation of the computer program listing in FIG. 8C.

FIG. 8E is a continuation of the computer program listing in FIG. 8D.

FIG. 9 is a graphical illustration of example of the output of thesimulation program illustrated in FIGS. 8A-8E.

FIG. 10 is an illustration of a typical simulation screen display thatcan be generated by the present invention.

FIG. 11 is a schematic drawing illustrating a single segment showerheadand system model described in the onscreen display illustrated in FIG.10.

FIG. 12 is a schematic drawing of an alternative embodiment of thepresent invention that utilizes optical sensing.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

The key to achieving highly controlled spatial distributions ofimpinging gas fluxes is to prevent or at least substantially minimizeintersegment mixing of gas flows. Such mixing of gas flows has been acommon problem encountered in prior known devices such as illustrated inFIG. 1. The device illustrated is a three-zone showerhead for CVDprocessing using concentric annular gas inlet zones (from below)impinging on a wafer held above. The difficulty is that in order for theimpinging gas to exit, it all must traverse the wafer surface beforebeing pumped out around the edges of the wafer.

FIG. 2A is a schematic diagram of the prior art device illustrated inFIG. 1 (depicting the right half of a symmetric system) in awafer-below/showerhead-above arrangement. The gas inlet and outletconfiguration in FIG. 2A is the basis for the model used to calculatethe resulting flow patterns in this device as illustrated in FIG. 2B.While gas emerges from all three zones of the showerhead, the gas fromthe center zone (on left in the figures) must flow radially across theentire wafer surface before being pumped around the wafer edge and outof the reactor. FIG. 2B shows the results of calculations for the flowpatterns associated with the structure in FIGS. 1 and 2B, computed using(global) spectral methods to solve the reacting species componentconservation equations. When the total flow velocity through theshowerhead is held constant across the showerhead (to minimize mixingfrom shear-induced flow instabilities) and when the reactant species areintroduced through a single segment (with inert gas introduced throughthe other segments) it has been found that the reactant concentrationplume in the vicinity of the wafer surface is shifted considerably fromthe radial location of the source segment, as shown in FIG. 2B. Theextent of this shifting effect depends on the total gas feed rate, theshowerhead/wafer spacing, and other operating parameters, resulting inan inherent unpredictability of the effects of this design on filmdeposition properties.

The present invention is directed to gas delivery showerhead assemblyand related methods for CVD, plasma and other processing ofmicroelectronics. It is designed as a multizone segmented structurewhich enables impinging gas fluxes and compositions to be variedindependently as a function of position over the wafer/substrate.Segment-to-segment variations in partial or total pressure/gas deliveryrates can be made to adjust the impingement distribution in linear,radial, or more complex x-y patterns as desired. These patterns may bechosen to achieve process uniformity at a desired design point or tointroduce intentional across-wafer nonuniformity in order to carry outcombinatorial experiments in which regions of the wafer representindividual experiments at different process design points.

Each segment of the showerhead includes not only a gas inlet, but alsogas exhaust capability, so that a significant fraction of the exhaustgases may be drawn up and pumped out through the showerhead itself. Thisminimizes intersegment mixing prevalent in prior known devices andenables a high degree of spatial distribution control of the gas fluxseen by the wafer/substrate. The present invention also provides amechanism for spatially-resolved sensing of inlet and exhaust gasstreams for chemical sensing, process metrology and control, andprocess/equipment model validation.

The present invention also relates to plasma processes, in which anelectrical discharge is employed to excite a plasma involving the gasesintroduced into the process reactor in order to accomplish materialdeposition, etching, oxidation/nitridation, or other modification. Aparticularly preferred embodiment of the present invention will bespecifically discussed in connection with semiconductor chipmanufacturing from silicon wafers, but it should be understood thatcorresponding considerations and conclusions apply to flat paneldisplays, data storage disks and heads, optoelectronic systems, andother microelectromechanical devices

As will be described in more detail to follow, embodiments of thepresent invention also involve supplementary features, including but notlimited to: mechanisms to adjust the dimensions of the showerheadelements and spacing with respect to the wafer/substrate surface; gasdistribution and pumping manifolds for the showerhead; chemical andpressure sensors, as well as flow actuation devices; modeling andsimulation methods for showerhead design, combinatorial processdevelopment, and process learning from data acquired; mechanical designswhich enable efficient showerhead fabrication and assembly; and designscaling strategies to achieve showerhead designs with higher spatialresolution (more segments) and lateral extent (for largerwafers/substrates) using meso-scale and microscale components.

Referring specifically to FIGS. 3A, 4, 5 and 7, certain preferredembodiments of the present invention will now be described. Shown inFIGS. 3A, 5 and 7 and generally designated by the reference character10, is a single-wafer process chamber that is utilized for performingvarious fabrication processes on semiconductor wafers. As illustrated,chamber 10 is only partially illustrated as encompassing the multizoneprogrammable showerhead 12. The chamber includes a process energy source14 which is preferably a heat or a plasma generation source that isdesigned to perform uniform process over a wafer 16. A heat source isusually used in thermally activated processes such as chemical vapordeposition processes. Other process energy sources such as plasma may beemployed during other fabrication processes, such as plasma etch andplasma enhanced chemical vapor deposition.

The wafer 16 is supported in an appropriate manner on a stage 18 that isselectively movable to position the wafer 16 a desired distance from theshowerhead 12. The stage 18 may incorporate the previously describedenergy source 14. The process chamber 10 is further provided with a gatevalve 20 that can be selectively utilized to exit gases from the chamber10. The wafer 16 may be clamped against a heated and/or radio frequencypowered chuck or it may be supported on several pins without anyclamping. The process chamber is well known in its structure and istherefore not shown or described in detail herein.

In preferred embodiments, the multizone showerhead 12 consists of anumber of zones or segments 22. Each of the segments 22 has a peripheralwall 24 defining its shape and an interior cavity 28. Each segment 22 ispreferably open at its top and bottom as illustrated in FIGS. 4 and 5.Alternatively, a plate 25 can be provided over a portion of the cavity28 as illustrated in FIG. 3A. Each segment further includes at least onegas inlet 30 and one gas outlet 32. The gas inlet can be provided withthe ability to deliver one or multiple flows of gas simultaneously tothe cavity 28. This is accomplished by providing a plurality of conduits26 that extend into the cavity of each segment 22, with the length ofeach segment is less than that of the wall 24. The conduits 26 may bepositioned against one another, as illustrated in FIG. 5, or spaced fromone another, as illustrated in FIG. 7. The geometry of the conduits canbe tubular or can replicate the geometry of the peripheral wall 24 ofthe segment 22.

As illustrated in FIG. 5, the conduits are part of a fluid control anddistribution network associated with the showerhead 13. As generallyindicated by the reference number 13, the flow control and distributionsystem provides a way of connecting the showerhead 12 with a variety ofprocess gases. The conduits 26 extend from the interior 28 of eachsegment 12 to a feed gas manifold 15 that contains a plurality ofcontrol valve assembly 17 for regulating the flow for each of therespective conduits 26. The manifold 54 is in turn preferably connectedto mass flow controllers 19 which selectively regulate the flow of eachparticular gas to each of the conduits 26 and segments 22. Gas issupplied to the mass flow controllers 19 from a gas storage 21. Thecontrol and distribution network 13 can provide separate supplies ofmultiple process gases to each of the segments 22.

The amount of gas supplied to each segments 22 can be the same or can beintentionally varied. Typical process gases which might be utilizedwould be, for example, hydrogen, argon, silane (SiH₄), tungstenhexaflouride (WF₆). Depending on the process, the number of inputprocess gas channels and the number and type of gases may vary. Thedesired gas flow rates through the system 13 can be varied both prior toand during the execution of any process within the chamber 10. Gas typesand volume can be supplied equally to each segment or in any disparateratio desired. The flow of gases through the system can either becontrolled manually or automatically using known methods. Additionally,the operation of the system 13 can also be dependent upon gas analysisdata collected from sensors in the showerhead 12 which will be describedbelow.

The gas outlet 32 can take the form of one or more openings in the outersurface, preferably at or near the top of the wall 24, of each segment22. In preferred embodiments, the gas outlet 32 of each segment 22extends around the top of the segment from the outer periphery of theinlet 30 to the gas inlet 30 peripheral wall 24 of the segment 22 asillustrated in FIGS. 4, 5 and 7. The gas exiting the cavity 28 of eachsegment through the gas outlet 32 exits preferably enters into a centralexhaust chamber 34. The chamber 34 in turn exhausts gases from thesystem through one or more ports 35. In an alternative embodiment, thegas outlet 32 of each segment 22 can exhaust the gas into one or moreconduits (not shown) rather than the chamber 34.

In the present invention, exhaust gas pumping as well as reactant gasinlet are implemented within each of the segments 22. In this way theflow pattern of the overall showerhead brings a substantial portion ofthe gases back from the reaction region at the surface of the waterthrough the showerhead 12. This has the effect of significantly reducingintersegment mixing, in that a much smaller amount of exhaust gastraverses the wafer surface below the dividing walls of neighboringsegments, compared to the behavior of the prior art devices illustratedin FIGS. 1, 2A and 2B. In other embodiments of the present invention,exhaust gas may be selectively extracted through the showerhead 12 usingonly some of the segments 22, achieving a portion of the full advantage.

FIG. 3A illustrates an exemplary structure of an individual showerheadsegment 22, which includes a gas inlet and the exhausting of gas fromthe region above the wafer 16 back through the showerhead segment 12.One primary advantage of the proposed showerhead design is the increasedactuator resolution attainable with this configuration. Gas fed andexhausted in each segment effectively results in the creation ofperiodic boundary conditions for the flow field at each segment wall 24.The computed flow field for two neighboring showerhead segments 12 isillustrated in FIG. 3B. This flow field further demonstrates thatintersegment transport of reacting species by diffusion can becontrolled by adjusting the height of the showerhead assembly from thewafer surface. The controllability of intersegment mixing afforded bythe segments 22 of the showerhead 12 is exploited in achievingacross-wafer uniformity. It will be appreciated by those of skill in theart that the benefits of the recirculating showerhead design equallyapply in CVD equipment configurations where the wafer is located eitherabove (FIG. 1) or below (FIGS. 3 and 5) the showerhead assembly.

The peripheral wall 24 of each showerhead segment 22 preferably has ashape that permits close packing of the segments 22 across theshowerhead. A wide variety of geometries, including square or circularshaped segments, can be utilized. A particularly preferred geometryutilizes hexagonal shaped segments. For each segment 22, inlet gas isdelivered to the wafer surface region at or near the center of thesegment 22, while exhaust gases from the reaction region just at orabove the wafer surface are pumped back up through the segment 22 to achamber 34 with a showerhead by an external pumping system. With thesegments 22 in close proximity to the surface of the wafer, as inconventional showerhead designs, the spacing between the bottom of thesegment perimeters and the wafer surface determines the relative role ofpumping through the showerhead compared to pumping around the waferedge.

The segmented design of the showerhead 12 optimizes the density ofsegments 22 in an x-y addressable array, making possible spatialprogrammability of impinging gas flux in radial, linear, and morecomplex patterns across the wafer 16. The showerhead segment 12 isdesigned as a fundamental modular building block that can be readilyexpanded and assembled to meet the lateral dimensionality required bythe product, whether an 8 inch wafer, a 12 inch wafer, or a larger flatpanel display. As an extendable structure built from a fundamental unit,the segmented design of the showerhead can extend equipment lifetime andusage of the showerhead. Some or all of the segments 22 can be preformedas an integral unit from stainless steel or similar materials.Alternatively, each segment 22 can be completely modular with anappropriate connecting mechanism on the outer portion of the wall 24 topermit segments to be selectively attached to or uncoupled fromneighboring segments. Optional spacers can also be provided betweenneighboring segments if desired.

Under typical operating conditions, heat transfer up through thesegmented showerhead 12 introduces no additional temperature-inducedconvection or other adverse effects compared to known conventionalshowerhead designs. FIG. 3C illustrates exemplary temperature field forthe present invention that corresponds to the operating conditions thatproduce the flow field illustrated in FIG. 3B. Furthermore, the completeshowerhead assembly may also optionally incorporate activeheating/cooling mechanisms to prevent reactant gascondensation/reaction.

The modular design of the showerhead 12 provides the additional benefitsof accommodating the use of in situ process sensors and therebysimplifying spatial monitoring of residual gas composition. FIG. 5illustrates three segments 22 of a seven segment system arrangementwhich are combined to form a multisegment showerhead 12 as previouslydescribed, that also analyzes exhaust gases from segment 22 to obtain ameasure of the reaction rate as a function of position. Downstream gassampling using chemical sensing techniques like mass spectrometry havealready demonstrated an ability to deliver deposition rate and thicknessmetrologies for CVD and plasma CVD processes. Any showerhead segment 12that it is desired to analyze exhaust gases from is provided with asampling gas exit 40. The exit is preferably located within the cavity28 of the segment 22 in close proximity to the wafer 16. Each exit 40 isconnected to a gas sampling capillary 42. The gas to be sampled ispumped through the sampling capillaries 42 and to a gas analyzer 44using a multiplexing device 46. A wide variety of known multiplexers andgas analyzers can be effectively utilized in connection with theshowerhead 12. A Leybold Inficon Composer and mass spectrometer havebeen found to be effective for use in connection with the presentinvention.

Turning now to FIG. 12, another embodiment of the present invention isdisclosed where the showerhead 12 is provided with an integrated in situoptical sensing capability. In this embodiment, each of the segments 22of the showerhead 12 is provided with both an illumination source 36 andan optical sensing element 38. This permits multipoint optical sensingsuch as full wafer inferometry and spatially resolved processmeasurements from each segment 22 can be evaluated in real time. Thisinformation can be combined with the data from a gas pumping and sensingsystem referred to generally as 41, as previously described. The opticalsensing data from that system can be provided to a control computer foranalysis and modeling as will be described below.

The ability to monitor across-wafer uniformity and real time sensing ofprocessing effects is crucial to the present invention to achieve newlevels of control and efficiency in semiconductor manufacturingprocesses. The use of in situ sensors which provide real time measure ofexhaust gases in each of the segments 22 of the showerhead 12 along withpost-process measurement of across-wafer properties, provide the basisfor exploiting advanced modeling methodologies. Integrated modelreduction and validation methods benefit from CVD or plasma processsystems designed to facilitate model development. Simulator developmentconsists of a three-step procedure: (1) posing a model structure basedon modeling those chemical and transport processes that can beaccurately characterized; (2) transforming the modeling equations toreduced by discretization; and (3) using this reduced model in aniterative (nonlinear) parameter identification technique to identifymodel components that may be difficult to determine otherwise. The finalstep makes use of both in situ (gas sampling and temperaturemeasurements) and ex situ data (deposition thickness, sheet resistance,material phase composition). The reduced models produced by thismethodology are used for model-based process control, processoptimization, and real-time simulation. This ability obviates the needin prior devices to utilize multiple wafers, reprogram the system, andconduct multiple set-ups to conduct such testing. Even with suchefforts, prior devices still could not achieve the highly controlledspatial distributions without significant index segment mixing of thepresent invention.

The ability to precisely control the processing in each particularsegment 22 of the showerhead 12 and monitor the processing in eachsegment in real time through analysis of exhaust gases and/or opticalsensing permits much greater accuracy, speed and economy in dynamicsimulation and optimization of equipment design and processes. FIGS.8A-8E illustrate a preferred example of a computer program listing foranalyzing the segment by segment data that can be realized from thedesign of the present invention and converts that into a system model.FIG. 9 represents a typical example of a graphical output of thesimulation program illustrated in FIGS. 8A-8E that can be generated.This output maps the effect of various processing parameters in aplurality of segments across a single wafer on the thickness anduniformity of the film deposited on the wafer thereon in threedimensions. FIG. 10 illustrates a typical screen display that can begenerated utilizing a computer simulation program and data from thepresent invention. FIG. 11 is a schematic drawing of a single showerheadsegment and system model of the type that is referred to in thesimulator screen illustrated in FIG. 10. It will be understood by thoseof skill in the art that the modeling and simulation program and outputillustrated and described herein is merely exemplary and that manyvariations are possible and are also within the scope of the presentinvention.

With the segmented showerhead design, exploiting exhaust gas pumpingthrough the showerhead 12 as well as a flexible spatial gas impingementpattern, highly controlled spatial distributions are achieved for CVDand plasma processes. This has two profound consequences. First, thehighly controllable design enables significantly increased processuniformity across the substrate or wafer over a broad range of desiredprocess design points, thereby achieving compatible co-optimization ofboth materials and manufacturing performance. Second, it achievesaccelerated experimentation and process development by also enablingcontrolled nonuniformity across the wafer so that combinatorial methodsprovide information on multiple experimental design points in eachactual experiment. This ability is very important since it permits theability to test and monitor in real time the materials, consequences ofa variety of different process parameters at different locations on asingle wafer at the same time.

Referring now to FIG. 6, use of the segmented programmable showerhead 12of the present invention for rapid process development and optimizationis schematically illustrated. In this embodiment, the showerhead 12 isprovided with seven hexagonally shaped segments 22 (designated as A-G inFIG. 6) that are arranged in order to maximize coverage over a circularwafer 16. Due to the significant reduction or elimination ofintersegment mixing between the segments, some or all of the respectivesegments A, B, C, D, E, F and G, can be intentionally programmed to havenonuniform processing parameters as indicated in box 44, that are notaffected by the processing parameters of neighboring segments. Byprogramming in intentional across wafer nonuniformity as described, alibrary wafer 46 is created which reveals the materials consequences ofvarious process parameters present in the segments A, B, C, D, E, F andG respectfully, which are at different positions on the single wafer 46.This functionality, along with the ability to adjust and achieve closewafer/showerhead spacing permits the granularity of the library wafer 46to be controlled within a range spanning sharply defined structures suchas the hexagonal region depicted in FIG. 6.

Alternatively, by manipulating the space between the showerhead and thewafer, continuously graded wafers that show the effect of gradations ofthe nonuniform process parameters in the neighboring segments can alsobe tested on the single library wafer 46. Once the desired materialproperties are identified and associated with specific processconditions, the showerhead assembly and reactor are reprogrammed toproduce uniform films, as indicated in box 48, that have the desiredmaterials properties from the selected segment from the library wafer 46across the entire wafer surface. This ability is illustrated in FIG. 6in creation of production wafers 50A, 50B and 50C, respectively, whichrepresent wafers having uniform thin film across the entire wafersurface corresponding to the process conditions of the correspondingsegments A, B and C, respectively, of the library wafer 46.

This programmed nonuniformity scenario represents a major advance beyondthe conventional approach to process development, particularly wellsuited to the complexity challenge of new materials and processes andleveraged by both the technology innovation described here and by thecombinatorial approach to materials and process discovery.

The capabilities of the present invention illustrated in FIG. 6 alsorepresent a major benefit of the segmented showerhead of the presentinvention for existing processes. As manufacturing goes through a rapidsequence of product enhancements, individual processes must often beadjusted and reoptimized to raise yields for the revised process flows,a requirement of process integration. For some important cases, theprocess design point desired for enhancing product performance may beknown, but uniformity is inadequate to achieve manufacturing yield. Inthis case, returning of the gas flux distribution from the segmentedshowerhead may be the only step required to obtain adequate uniformityat the desired process design point.

While embodiments have been described herein employing conventional gasflow components, other components and system arrangements may be moreefficient and cost-effective in more sophisticated embodiments whichachieve higher spatial resolution across the wafer and/or largerwafer/substrate sizes. Other embodiments of the present invention alsohave additional characteristics which will further facilitate scaleup tolarger numbers of independently controllable showerhead segments, largerwafer or substrate size, and higher spatial resolution and control.Spatial distribution of inlet and exhaust gas channels, as well assensor and control means, may be accomplished through a more integratedassembly such as using vertical and horizontal channels in a mechanicalstructure. With the rapid development of microelectromechanical systems(MEMS) technology, another embodiment of the present inventionincorporates MEMS devices into the showerhead, in the form of chemicaland optical sensors, pressure sensors, temperature sensors, actuatorsfor flow control, and integrated control systems. Scaleup to largerwafer or substrate size is further facilitated by the use of independentmodular showerhead segments which can be readily interconnected and toachieve showerheads as large as required, with each segmentincorporating gas inlet and exhaust, sensors, actuators, and controlmeans, along with interconnections automatically made to thecorresponding facilities in neighboring segments.

The preferred embodiments described herein relate primarily totwo-dimensional distributions of programmable showerhead segments. Suchdesigns are appropriate for the preponderance of practice in currentsingle-wafer processing tools. However, in some cases a one-dimension(linear) distribution of segments may be useful as well, in which thewafer or substrate may pass under the linear showerhead during theprocess. Although such linear designs have seen limited use, they mayhave advantages particularly for producing uniform coatings on largesubstrates.

The embodiments described above provide solutions that achieve asubstantially higher degree of control of process uniformity andaccelerate the process development and optimization cycle by minimizingthe experimentation required. By enabling independent control of thespatial distribution of gas fluxes in independent showerhead segments,it is possible to achieve across-wafer uniformity at whatever nominalprocess parameter design point is desired, thereby improving materialsand product quality and manufacturing yield. This overcomes the currentobstacle by which materials and process performance must be a tradeoffagainst the across-wafer uniformity of the process.

Furthermore, spatial programmability of gas fluxes will also enable thegeneration of intentional across-wafer nonuniformities. This willfacilitate rapid experimentation and process optimization in knownmaterials systems. It will also accelerate materials and processdiscovery, which is particularly important for the major challengesposed by future technology requirements.

The programmable nonuniformity feature of the present invention mayprovide benefit in other situations as well, even where the processtechnology is well known. Many chemical processes exhibit dependence onpattern factors, where process rates or topography vary with the densityof patterns on the wafer. In chip designs which involve relatively largeregions of one pattern (e.g., memory chips), it may be possible toproduce a first-order correction for pattern factor dependence utilizingprogrammable nonuniformity. Another possibility is that programmablenonuniformity could be used to manufacture wafers with different chipdesigns at different positions on the wafer, e.g., needing differentlayer thicknesses on different chips.

The present invention is also believed to be applicable to atomic layerdeposition (ALD), as well as to conventional CVD and plasma processes.ALD is drawing great interest because of its ability to achieve highmaterials quality and process reproducibility. It exploits theself-limiting adsorption of reactants on the surface, exposing thesurface to reactants sequentially rather than in parallel. The spatiallyprogrammable showerhead described herein is relevant to ALD in severalways. First, while ALD may improve across-wafer uniformity (as well asconformality over 3-D microfeatures), the spatially programmableshowerhead could add the benefit of rapid experimentation through use ofintentional nonuniform ALD across the wafer. Second, the dominance ofexhaust gas pumping through the showerhead segments (compared to themain reactor pumping system) may provide the rapid gas exchange neededbetween reactant exposure steps to achieve high throughput in ALD, whichis normally a low rate process.

Having described various embodiments of the invention, it will beunderstood that many changes and modifications can be made theretowithout departing from the spirit or scope of the invention.

What is claimed is:
 1. A multizone gas injector and distributionshowerhead for use in microelectronics substrate processing andequipment, comprising: a plurality of separately programmable segments,each of said segments having a wall with a first end located inproximity of the substrate and a second end spaced from said substrateand an internal cavity between said first and second ends within saidwall; a gas inlet associated with each of said showerhead segments thatintroduces gases for processing into said cavities; and an exhaust gasoutlet associated with each of said showerhead segments, said gas outletincluding selectively actuatable removal of some of the exhaust gas fromsaid cavities of said segments through a portion of said showerheadsegments other than said first end.
 2. The device of claim 1, whereinsaid exhaust gas outlet is selectively programmable to removeindependently variable amount of gas from each of said plurality of saidshowerhead segments.
 3. The device of claim 1, wherein said exhaust gasoutlet removes some gas from all of said showerhead segments.
 4. Thedevice of claim 1, wherein said plurality of showerhead segments arearranged to enable a variety of gas impingement patterns, includingradial and linear distributions.
 5. The device of claim 1, wherein saidplurality of showerhead segments are arranged to enable a variety of gasimpingement patterns, including radial, linear and nonradial, nonlinearx y distributions.
 6. The device of claim 1, wherein said segments aremodular and can be selectively connected and disconnected.
 7. The deviceof claim 1, wherein the spacing between said showerhead segments can bemodified.
 8. The device of claim 1, further comprising means foradjusting the distance between the substrate and said gas inlet.
 9. Thedevice of claim 1, further comprising means for adjusting the distancebetween the substrate and said exhaust gas outlet.
 10. The device ofclaim 1, further comprising means for adjusting the distance betweensaid segments and the substrate.
 11. The device of claim 1, wherein saidgas inlet further comprises a plurality of inlet conduits and arrangedto be connected to at least one source of process gas, wherein saidsource of process fluid is capable of providing a combination ofdifferent process gases to said inlet.
 12. The device of claim 11,wherein said type of combination of said gas and the pressure and volumeof gas can be selectively controlled.
 13. The device of claim 12,wherein said type of combination of said gas and the pressure and volumeof gas can be independently varied from one segment to the next.
 14. Thedevice of claim 1, further comprising sensors, at least one sensorassociated with each of said segments for sensing process parameterscharacteristic in that segment.
 15. The device of claim 1, furthercomprising at least one sensor associated with each of said segments forsensing process parameters characteristic between the substrate and eachsegment.
 16. The device of claim 14 or 15, wherein said sensors includethe ability to sample for chemical species, or pressure and generatesignals corresponding to these parameters to a central receivingstation.
 17. The device of claim 16, further comprising actuators toindependently modify conditions in respective segments in response tothe signals received by the central receiving station.
 18. The device ofclaim 17, wherein said actuators can modify gas flow pressure andtemperature within each of said segments.
 19. The device of claim 1,further comprising an optical sensing device associated with each ofsaid segments that conveys light from a remote source to the cavity ofthe segment or to an area of the substrate surface; means for returninglight from these areas to an optical detection system for receivinglight from said light returning means.
 20. The device of claim 15 or 16,means for processing the signals from said sensors and creating a modelof the effects of processing parameters on the substrate.
 21. The deviceof claim 19, a processing means associated with said optical detectionfor creating a model of the effects of processing parameters on thesubstrate.
 22. The device of claim 1, wherein each of said segments arehexagonally shaped.
 23. A multizone gas injector and distributionshowerhead for use in microelectronics substrate processing andequipment, comprising: a plurality of separately programmable modularscalable segments, each of said segments having a wall with a first endlocated in proximity of the substrate and a second end spaced from saidsubstrate and an internal cavity between said first and second endswithin said wall; and wherein showerhead segments to can be selectivelyjoined and removed to enable a variety of segment patterns, includingradial and linear patterns.
 24. The device of claim 23, wherein saidshowerhead segments are arranged to enable gas impingement patters,including nonlinear x-y distributions.
 25. A method of processing amicroelectronics substrate using a multizone gas injector distributionshowerhead having a plurality of programmable segments, comprising thesteps of: selectively positioning the showerhead in close proximity tothe substrate; introducing a gas into each of the showerhead segmentsthrough one end of said segments, selecting the amount of exhaust gasdesired to be removed from each of said segments; and removing exhaustgas from the same segment that said gas was introduced into in responseto the selection made in said selection step.
 26. The method of claim25, wherein said removing step involves removing exhaust gas from onlysome of said showerhead segments.
 27. The method of claim 25, furthercomprising the step of impinging the gas from each of said segments ontothe substrate in a consistent radial distribution.
 28. The method ofclaim 25, further comprising the step of impinging the gas from each ofsaid segments onto the substrate in a consistent linear distribution.29. The method of claim 25, further comprising the step of impinging thegas from each of said segments onto the substrate in a consistentnonlinear, nonradial x-y distribution.
 30. The method of claim 25,further comprising the steps of selectively connecting said showerheadsegments prior to gas introduction.
 31. The method of claim 25, furthercomprising adjusting the distance between the substrate and the point atwhich gas is introduced into said segments in said introducing step. 32.The method of claim 25, independently adjusting the type, pressure andvolume of gas introduced in said introducing step.
 33. The method ofclaim 25, sensing process parameters characteristic in each of saidsegments.
 34. The method of claim 33, wherein said sensing step includessensing chemical species, pressure, temperature or volume.
 35. Themethod of claim 25, optically sensing an area of the substrate surface.36. The method of claim 25, further comprising means for adjusting thedistance between the substrate surface and the gas exhaust in thesegments.
 37. The device of claim 1, wherein the type or combination ofgas can be independently varied from one segment to the next.
 38. Thedevice of claim 11, wherein the gas flow rate and composition can bevaried independently from one segment to the next.
 39. A multizone gasinjector and distribution showerhead for us in microelectronicssubstrate processing and equipment, comprising: a plurality ofseparately programmable segments, each of said segments having a wallwith a first end located in proximity of the substrate and a second endspaced from said substrate and an internal cavity between said first andsecond ends within said wall; a gas inlet associated with each of saidshowerhead segments that introduces gases for processing into saidcavities; and a selectively actuatable exhaust gas outlet associatedwith each of said showerhead segments that removes some of the exhaustgas from said cavities of said segments through a portion of saidshowerhead segments other than said first end.
 40. The device of claim1, wherein the distance between said gas inlets and said first end ofsaid segments is adjustable.
 41. The device of claim 1, wherein thedistance between said gas outlets and said first end of said segments isadjustable.
 42. The device of claim 14, wherein said sensors senseexhaust as in said segments.
 43. The device of claim 25, furthercomprising the step of sensing the characteristics of the exhaust gasremoved in said removing step in at least one segment.
 44. The device ofclaim 43, wherein said sensing step is done in real time.
 45. The deviceof claim 25, further comprising the step of sensing the characteristicsof the exhaust gas removed in said removing step in said segments. 46.The device of claim 25, further comprising independently adjusting thecomposition, pressure or flow rate of gas introduced in each segment insaid introducing step.
 47. A method of processing a microelectronicssubstrate using multizone gas injector distribution showerhead having aplurality of programmable segments, comprising the steps of: selectivelypositioning the showerhead in close proximity to the substrate;introducing gas into each of the showerhead segments through one end ofsaid segments; exiting gas from said showerhead segments toward saidsubstrate; and removing exhaust gas through at least one of saidsegments that said gas was introduced into.
 48. The device of claim 1,wherein each of said gas inlets is separately selectively actuatable.49. The method of claim 48, wherein said removing step further comprisesminimizing intersegment mixing of gas along said substrate.
 50. Themethod of claim 25, wherein said introducing and removing steps providea symmetry of exhaust gas about the point of introduction of said gas ineach segment.
 51. The method of claim 48, whereby said introducing andremoving steps further comprise steps providing a gas impingementdistribution on said substrate that is controllable in two lateraldimensions.
 52. The method of claim 48, wherein said introducing andremoving steps further comprise providing selective uniformity ornon-uniformity of gas impingement on said substrate from segment tosegment.